The 25-year-old has seen eight players sign for the Black Cats already this summer, including the likes of USA international striker Jozy Altidore.
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"Over the last couple of days, everyone has bonded well by sharing rooms with each other. We're getting on well.
"It's tough at times, being away for long periods with morning and afternoon sessions, but you've got to keep focused and do the work because at the end of it we're going to be the ones who benefit."
Manager Paolo Di Canio has had the players in Italy for a pre-season training camp before they head over to Hong Kong for preparatory matches.
"It's been very tough in this heat but that's what we've got to do," Johnson remarked.
"I remember doing a few tough ones in my time at Middlesbrough but this one is right up there with the toughest, even though we're only a week into it. Hopefully we'll get the benefits from it at the end."